The system then frees the locations in memory occupied by the process so it can be used by other processes (Master).
During the lifetime of a process it will use many system resources. It uses the processor to run its instruction and the system's physical memory to hold its data. If the process involves an I/O instruction it may directly or indirectly use the physical devices of the system. Linux must keep track of the process and not let one process monopolize the processor.
When a process is using the processor, it's actually running and doing work, but it will not always stay in that state. If a process contains an I/O instruction, but the device is not ready, the process is blocked. In a multitasking environment a process is not allowed to use the processor all the time. A process will be stopped at intervals so that another process can run. In this state it is not running, but is runnable (or ready) and is simply waiting for the processor to give it its time-share (Newmarch).
The operating system also maintains information about each process in a process table. Entries or listings in the table are called process control blocks and contain information about process state, memory state, and resource state.
Microkernels, Threads, and SMP:.
In Linux the core program of the operating system is the kernel. The kernel manages the schedule of tasks undertaken by the processor, allocates primary memory, and handles I/O tasks .
to terminals, disk drives, and other peripherals. The kernel is the basic interface between the shell the device drivers and hardware. .
Earlier versions of Linux featured a large single kernel. Later versions of Linux and most new Unix operating systems have gone to a microkernel architecture. Instead of having one large kernel to control the program, it is broken down into small microkernels. Each of these microkernels are assigned a few essential functions within the kernel itself.
